The physical version of Something Only They Would Say, where a character is identified by an unusual body deformity or trait, like a mole or birthmark. Bonus points if the mark is in a place that would be embarrassing/forbidden to show in public.
The barcode (which may be a tattoo but probably isn't) is often used as a sci-fi variation on the birthmark.
See also Scars Are Forever. For a Distinguishing Mark that marks the Chosen One, see Birthmark of Destiny. If the Distinguishing Mark shows that the character is supernatural or magical, it's Mark of the Supernatural. If the Distinguishing Mark shows that the character is or was a slave, it's a Slave Brand. If it is meant to show that a character is (or is assumed by others characters to be) evil, then it's the Red Right Hand. Overlaps with Facial Markings if it's located somewhere on the face.
- Subverted in Mermaid Melody Pichi Pichi Pitch, when Tarou notices a mermaid with Rapunzel Hair and is sure it must be Sara. It's not. All mermaids have long hair, and they otherwise looked nothing alike.
- In Chrono Crusade, Chrono's missing horns are so prominent that he's known as "Chrono of the Broken Horn" to some of the other demons. And, of course, Satella is searching for a demon without horns...But later it's revealed that Aion is missing his horns, as well.
- In Haruhi Suzumiya, Mikuru's mole on her left breast is the usual thing Kyon looks for when he wants to see if it's the "real" Mikuru. In the novels, Kyon once asked her to show it (to which she replied with a punch) and another time realized it was not her because of it.
- In Lucky Star, Konata looks identical to her mother, except for a birthmark under her eye (and her ahoge).
- Jacuzzi Splot from Baccano! is often immediately identified by the blue, oddly-shaped sword tattoo on his face - unfortunate for him, considering that he's got a large bounty on his head and more than a few enemies with an axe to grind.
- A meta-example in Higurashi: When They Cry: the identity of the corpse discovered at the beginning of Curse Killing Chapter is never revealed, but an astute-eyed viewer can figure it out for themselves if they spot the Distinguishing Mark — the red star-shaped tattoo on the left thigh identifies it as Rina Mamiya.
- Mai-HiME: The easiest way to identify a HiME is a fireball-shaped Power Tattoo on their body. It's in a different spot for each girl - Mai's is on her right breast, Natsuki's is on her lower back, etc. Akira also has one, but she hides it to maintain her disguise, and thus the other HiME don't know that she's one of them until much later.
- Kotetsu T. Kaburagi/Wild Tiger from Tiger & Bunny has a rather distinctive-looking goatee. In fact, it's so distinctive that it's implied that many people don't bother to remember what the rest of him looks like.
Security Guard: "With that beard and mask, anyone could look like him!"
- Fullmetal Alchemist:
- Maria Ross has a mole under her eye. While about to kill Major Hughes, Envy pretends to be Lt. Ross. Envy however fails to replicate this mark when imitating her but she quickly fixes it.
- Also, Scar got his nickname because of the X-shaped scar on his forehead, courtesy of Kimbley. We never actually learn his true name, but the other characters needed something to call him by.
- The titular character has fuzzy, white dog ears on top of his head (not floppy ears like most dogs, more like the Shibi Inu◊ breed.) This marks his heritage as an inu-hanyou - half human, half dog-demon. He also his golden eyes with cat-like pupils, like his father.
- Most of the demons in the series show certain traits that tell them apart from humans, even when in humanoid form. These include pointed, elf-like ears, unusual coloration in their eyes and hair, and (sometimes) claws and fangs. If their true form has a tail, that will often be visible, since it apparently takes a lot of power to hide it. In Shippous case, hiding the tail is often a problem when he disguises himself using his fox-magic. (Shippou is a very young kitsune-youkai - fox demon. In Japanese folklore, foxes were said to be great tricksters, and the masters of disguise. Being so inexperienced, Shippou still isnt very good at shapeshifting, but hes getting better.)
- In Rurouni Kenshin, the Hitokiri Battousai is known for having red hair and a cross-shaped scar on his left cheek. In some places where he is less famous that gets shortened to just a cross-shaped scar. During part of the Kyoto arc he even covers it up with a bandage to avoid drawing attention.
- Meta example in Miss Kobayashi's Dragon Maid where the maid at the end of chapter 28 can be identified by the audience as the bandit girl due to the small scar on her right cheek. Taken further in the anime, since it's covered by her hair until the last second for The Reveal.
- In Empath: The Luckiest Smurf, Empath is distinguished from his fellow Smurfs by having a yellow star birthmark on his forehead, which according to their legend indicates that he has telekinetic and telepathic powers. Hefty in the series has a red heart birthmark on his right upper arm, but generally refers to it as a tattoo when he receives an identical mark on his left upper arm from Painter.
- Toy Story 2 uses this to distinguish the familiar Buzz Lightyear with an otherwise identical one fresh from the box. In addition to knowing that he's a toy, the familiar Buzz proves that he's the friend of Woody by lifting his foot, revealing "Andy" written on his sole that was put there by their owner.
- Hiccup in How to Train Your Dragon has a tiny scar on his chin. In How to Train Your Dragon 2, it is revealed he got the scar when he was clawed by a dragon as a baby. When Valka first confronts Hiccup she stops short when she recognizes his scar.
Valka: Hiccup? Could-could it be? After all these years? How is this possible?
Hiccup: Uh, should I... should I know you?
Valka: No. You were only a babe. But a mother never forgets.
- In Barbie in the Princess and the Pauper, Anneliese has a crown shaped birth mark on her shoulder that is used to distinguish her from Erika and prove that she is the real princess.
- In The Princess and the Pea, the court historian, Sebastian, makes a note that the newborn princess, Daria, had a heart-shaped birthmark on her left foot. This acts as a Chekhov's Gun to help identify her as the real princess later on.
- In The Princess Bride, Count Rugen is identified by his sixth finger on his right hand.
- There's a royal birthmark (the Purple Pimpernel) on the royal posterior of the true heir to the throne in The Court Jester. Danny Kaye's character gets to show the infant's bottom to everyone to gain their reverence.
- L.A. Confidential: A mother cannot initially ID her daughter in the morgue. The Coroner prompts her with Detective Lieutenant Exley and Officer Bud White hanging on her every word:
Coroner: Mrs. Lefferts, does your daughter have any distinguishing marks?Mrs. Lefferts: She has a birthmark on her hip. It's her. My baby!
- The scene won the 1998 Skinny Award for "Best birthmark used to further the plot".
- In Hong Kil Dong, Hong Kil Dong recognizes the bandit that tried to kill him when he was a child, by noticing the scar on the bandit's hand where young Kil Dong bit him.
- In The Inspector General the only thing which distinguishes identical twins Izzick and Gizzick is a strawberry mark on Izzick's right leg which he tries to exhibit as proof of identity several times, only to be stopped by the mayor. When he finally gets to show it off without interruption, it turns out to be on his brother's leg.
- In Charlie Chaplin film The Vagabond, the woman who was kidnapped as a child is recognized by a distinctive birthmark, seen when her mother views her portrait.
- The Goosebumps book "My Hairiest Adventure" has a character with one blue eye and one green eye — which turns out to be important after she's transformed into a dog.
- The Dragonlords of Joanne Bertrin's novels all have a distinguishing physical mark (birthmark, odd eyes, dwarfism, albinism) which indicates their Dragon natures. One of the clues that a young woman is not really a Dragon is that her mark can easily be hidden.
- Harry Potter
- Harry Potter and the Prisoner of Azkaban uses the missing toe on Scabbers's front paw thusly.
- In Harry Potter and the Deathly Hallows, Lucius Malfoy uses the scar on Harry's forehead to identify him, since Harry's face has been disfigured by Hermione's jinx.
- All of the Death Eaters have a Dark Mark branded on their arms.
- The Silence of the Lambs Hannibal used to have six fingers on one hand, more specifically a second middle finger. He has it surgically removed after Silence, but of course he retains his maroon eyes.
- The Sylver family line in Welkin Weasels all have a facial birthmark shaped like a lightning bolt.
- Conan the Barbarian:
- In E. Nesbit's Five Children and It, after the children foolishly wish that everyone would want their little brother and then have to chase after everyone who kidnaps him, one character claims him as his long-lost son because he doesn't have a birthmark.
- Edward Rutherfurd uses this trope a lot to distinguish between the families in his Generational Saga novels, variously giving them characteristics such as long toes, waddling gaits, or oversized noses. Played with a bit in London, in which the Ducket/Dogget line has three such traits: natural Skunk Stripe hair (both sexes), partially-webbed fingers (several of the males), or obesity that's probably linked to hypothyroidism (a few of the females).
- In the Judge Dee mystery The Chinese Maze Murders a father identifies his daughter's headless body by a burn on the arm that she got when she was just a toddler.
- The heirs to the throne of Riva in The Belgariad have a white mark on their palms, burned into their bloodline when Riva Iron-Grip carried the Orb of Aldur.
- In A Brother's Price, part of the Porter family is polydactyl, with an extra toe on one foot. This tips off Eldest Whistler to the paternity of Kij's daughter, Eldie, who was sired by Kij's brother Keifer. While Keifer was married to the princesses.
- The Mortal Instruments:
- Jace Wayland has a star-shaped mark on his shoulder which is a birthmark of the Herondale family.
- Simon gains the ability to walk in sunlight, nicknaming him "Daylighter" and the Mark of Cain, though he later loses the latter.
- In Veniss Underground, Nicola has a birthmark in the shape of a rose between the thumb and forefinger of her left hand. When Shadrach sees it on Lady Ellington's transplanted hand, he realizes that Quin has taken Nicola to his organ farm to be used for spare parts.
- In Half Bad, Nathan was tattooed so that he could be distinguished from other witches.
- A Song of Ice and Fire: When Cersei has but a price of Tyrion's head, the fact that he's a dwarf without a nose makes it very hard for headhunters to falsify their claims. Not that they don't try. They show up with the half-rotten heads of other dwarfs, with their noses cut off postmortem. Cersei is not impressed.
- In The Orphan's Tales, the Girl who narrates the tales has dark markings covering and surrounding both eyes. They look solid black from a distance, but seen close to, they're actually tiny, tiny words which she has read and memorized.
- Survivor Dogs: Blade stands out from the other Fierce Dogs by having a white mark in the shape of a fang near her neck. This same mark also appeared on a dead pup's neck, giving Lucky the hint that the puppy was Blade's child. In fact, Blade murdered him herself.
- The Hero Rohan in The Mystic Knights of Tir Na Nóg has a birthmark called the Mark of Destiny that his druid mentor and foster father takes as a sign proclaiming him to be The Chosen One. He's right... but the mark isn't unique to Rohan. His half-brother Lugad and the Big Bad Queen Maeve, their mother, also bear the Mark of Destiny.
- Ivar is in Kells hunting a thief who stole a sacred chalice from his people. He knows him only by a scar at his forehead. During a battle with Torc, Ivar knocks off the man's helmet to see the scar and realizes Torc is the thief. Torc openly boasts he drinks from that cup every night to anger Ivar who is dedicated to getting the chalice back.
- On an episode of Highlander, the widow of a Watcher wants to expose Immortals to the media. A newspaper publisher naturally doesn't believe her story of people who can live forever and engage in sword duels to the death. She shows him a database featuring a man the publisher knows as a powerful millionaire, noting the man's facial scar. She then begins showing photos of a variety of men over the decades, from World War II to the 1890s to the Civil War and the early 19th century. The publisher's jaw drops when he sees that, while the name, hair styles and clothing are different, each of these men has the exact same scar and realizes they're all the same man.
- Played for Laughs in the Monk episode "Mr. Monk Takes On Manhattan", Monk recognizes a tiny mole on the perp's ear. He then spends an absurd amount of time describing the ear to a sketch artist. Later, when interviewing a suspect, Monk tries to get a peek at his ear.
- In an episode of Hot in Cleveland, a mother and son are reunited in part by the son bearing a birthmark on his wrist in the shape of a handbag.
- In The Refugees, the time-traveling refugees carry a chip on their chests that shines a red light. It is also used to monitor them and make sure they don't break the rules.
- In this video for Avicii's "Wake Me Up", two girls (implied to be either mother and daughter or older and younger sisters) living on a farm each bear a birthmark or tattoo of two triangles (the Avicii logo), the older on her right arm, the younger on her left shoulder, and are clearly shunned by others in a nearby town. At one point, the older girl rides her horse to a neighboring town, where she meets other people with the Avicii logo mark on their bodies. They welcome her and take her dancing. The next day, the older girl tells the younger to pack her things, because they're going to a place where they belong.
- Parodied in the one-act opera Cox and Box by F. C. Burnand and Arthur Sullivan, in which Box declares that Cox must be his long-lost brother because he doesn't have a birthmark on his arm.
- Animal Crackers identifies Roscoe W. Chandler as Abie the fish peddler with a large birthmark on his arm. Ravelli and the Professor later steal a wide array of his possessions - the Professor gets the birthmark.
- Evergrace: in this game, people who bear the Crest—a series of markings that appear on one's hand—are often subject to misfortune. The fact that there's a magician, with an entire empire in his control, searching for Crest bearers as test subjects probably doesn't help matters.
- Professor Layton and the Curious Village: Flora Reinhold's disappearing-reappearing birthmark is the final clue Layton needs to solve the mystery of St. Mystere.
- In King's Quest III, the way Gwydion proves he's the long lost Prince Alexander is by showing Princess Rosella a birthmark he has in a rather embarrassing place.
- In several The Legend of Zelda games, the mark of the Triforce (see the featured image on the Rule of Three page) appears on the hands of three individuals. Ganondorf has the Triforce of Power, Princess Zelda has the Triforce of Wisdom, and Link has the Triforce of Courage. Each piece of the Triforce is represented by a different triangle - Power is on top, Wisdom is on the bottom left, and Courage is on the bottom right.
- In The Legend of Zelda: Twilight Princess, Link starts out with the Birthmark of Destiny on his left hand (right in the Wii version). Its also visible in his wolf form.
- In The Legend of Zelda: Breath of the Wild Paya is named after the papaya seed shaped birthmark "...smack in the middle of her left butt cheek!"
- With the exception of Mark Meltzer or the multiplayer characters, all of the playable characters in the BioShock games have a mark or deformity on their hands or wrists.
- While it's never pointed out, in BioShock, Jack has a tattoo of a ball and chain on his wrists, symbolizing the fact that he is a slave to Atlas/Fontaine.
- Subjects Delta and Sigma BioShock 2 have a Δ and Σ mark on their left hands, respectively. This were probably used to distinguish each model of the Alpha series.
- In BioShock Infinite, both leads have one of these. Booker DeWitt's right hand bears the mark of AD, (the initials of his daughter, Anna DeWitt, which he branded himself with after giving her up to wipe away his gambling debts) while Elizabeth has a missing phalanx bone on her right little finger, which she covers with a thimble. The reason for this is that said phalanx bone was cut off by a tear when she was an infant, thus allowing her to open tears.
- In Fire Emblem Awakening, the Exalted family of Ylisse has the Mark of Naga on their bodies and the Avatar has the Mark of Grima on his/her hand, which only fades away if he or she kill Grima themselves.
- Chrom has the Mark of Naga on his bare shoulder, and his elder sister Emmeryn has it on her forehead. Their little sister Lissa does not have the mark, however, so she fears that she's a bastard child until her Kid from the Future Owain appears and shows her his Mark.
- Lucina, Chrom's daughter, inherits the Mark of Naga as well: it's found in the iris of her left eye.. If her mother is Olivia, then her potential younger brother Inigo has the Mark in the iris of his right eye, and mentions it as proof of his heritage when recruited.
- Also mentioned in regards to Owain's Older and Wiser self Odin from Fire Emblem Fates. If he gets married and fathers Ophelia, she inherits the Mark of Naga too; the DLC's extend this to his other potential children, Shigure and Kana.
- In Juuzaengi, when Kakouton loses his eye and gets a fever from his injury, his only memory of his savior (Kan'u) is the mole on her arm.
- Nathan Hale in The Dreamer has a powder burn on his forehead and a mole on his neck.
- In Shinka The Last Eevee Luna the Umbreon has diamond-shaped rings for some reason, her brother Shadow has orange instead of yellow rings and their clan banished him because of them.
- Oliver of Lightning Made of Owls has an L-shaped scar as his distinguishing feature.
- Mari from Moxie has a tattoo mark on the inside of her right wrist, distinguishing her as a noble.
- Sailor Nothing: Himei sports a black eye in Chapter 2; as she turns out, she can't Clark Kent her way around it.
- This webpage on basic Time Travel points out that even identical twins or clones won't have the same moles or skin tags, so this is a good way to convince people you really are them-self from a parallel universe.
- G.I. Joe: A Real American Hero: The difference between the mirror image Tomax and Xamot? Xomat has a scar on his left cheek. For twins that share a link, it was no doubt agonizing for Tomax.
- Dipper of Gravity Falls apparently has a birthmark on his forehead that looks like a certain constellation that answers certain questions. He mentions that kids made fun of it before he started covering it up.
Wendy: The Big Dipper! That's how you got your nickname! I thought your parents just hated you or something.
- The author, as described by the shapeshifter as "a six-fingered nerd", is in fact polydactyl, with his hand being used as his emblem on his journals. Notably this is the most obvious physical difference between himself and his twin brother Stanley Pines.
- The Penguins of Madagascar: Rico has a scar on the right side of his face.
- Krusty the Clown in The Simpsons has a pacemaker scar, a cattle-skull birthmark, and a superfluous third nipple on his chest.
- In All Hail King Julien, an Identical Stranger tries to take Julien's place, and Clover is able to identify the real Julien by identifying the supposedly bad scar on his butt he got in the first episode.
- During the Monica Lewinsky scandal, the "distinguishing characteristic" of President Clinton's private parts used to back up her claim that he did have sex with that woman.